Abstract: The invention provides an activated silica enriched mazzite having a chemical formula in the anhydrous state, expressed in molar ratios of:a M.sub.2/n O; Al.sub.2 O.sub.3 ; b SiO.sub.2 ;with a variation from 0 to 0.5, M being an alkaline cation of valency n and b being greater than 7, and which has an acid strength corresponding to an amount of heat measured by ammonia absorption microcalorimetry, greater than 190 KJ/mol, and a pore volume, measured by cyclohexane adsorption, greater than 0.09 ml/g. The activated mazzites are useful in the conversion of hydrocarbons, in particular, the isomerization of C.sub.4 to C.sub.8 paraffin, and as molecular sieves in processes for the separation of hydrocarbons.

Abstract: Process for the synthesis of a silica-enriched crystalline aluminosilicate having the offretite structure from a nucleation gel A containing sources of silicon, aluminium, alkali metal ions, an organic structuring agent and water and a growth gel B containing sources of silicon, aluminium, alkali metal ions and water. The crystals formed are calcined, the ions are replaced by protons and the crystals are subjected to a hydrothermal treatment followed by a treatment with a strong mineral acid. The aluminosilicate formed has a good selectivity in acid catalysis reactions and is characterized by its good stability.

Abstract: Process for the preparation of a crystalline aluminosilicate enriched in silica, having the structure of mazzite, by hydrothermal crystallization of a gel containing sources of silicon, aluminum and alkali metal ions, in the presence of an organic structuring agent, characterized in that the source of aluminum is a zeolite Y in the form of spheres. The mazzite obtained does not contain any silicoalumina debris out of the lattice. It is employed as catalyst for the conversion of hydrocarbons or as molecular sieve.

Abstract: A process for the preparation of bitumen-polymer compositions, characterized by the fact that the bitumens are modified by grafting of a dihalopolybutadiene polymer that serves as a receptive structure to block polymers and to elastomers co-vulcanizable with the grafted bitumen.The elastomers are selected from the group that includes linear polybutadiene-polystyrene block copolymers, a polystyrene-polybutadiene block copolymer, and a vulcanizable polynorbornene rubber. They are used as road and industrial bitumens.